textproduct: Quad Cities

KEY MESSAGES

- A storm system passing through the Upper Midwest this evening and Wednesday will bring widespread showers and storms to the area. Severe storms and heavy rainfall with the potential for flash flooding will be possible in eastern Iowa.

- Quiet weather Thursday into Friday, as high pressure passes overhead. Seasonal conditions will remain, with mostly clear skies.

- Another stretch of potentially active weather this weekend into the next work week, bringing daily chances of precipitation for some.

SHORT TERM /THROUGH WEDNESDAY/

Issued at 303 AM CDT Tue Sep 8 2026

Water vapor imagery shows a shortwave trough moving into southern Saskatchewan early this morning. As it is doing so, low level flow across the central Plains has become southwesterly. Warm advection along this axis and a strong LLJ is bringing in a warm, moist airmass that is supporting several clusters of showers and storms from Kansas to Minnesota. As this airmass moves into eastern Iowa and northwest Illinois this morning, these showers are expected to decay as they encounter dry air and a dying LLJ.

Any remaining cloud debris and remnant showers will help keep high temperatures north of Highway 30 in the 80s. South of Highway 30, highs in the low to mid 90s are expected with peak heat indices in the 90s. However, these peak heat indices are expected to last for only a few hours, which should limit any major impacts.

Of greater concern is the potential for widespread showers and thunderstorms this evening through midday Wednesday. Moisture advection throughout the day will bring in PWATs of 2.00+ inches ahead of a slow-moving cold front. Weak forcing ahead of this boundary will support the development of showers and storms this afternoon across central Iowa. Modest instability of 1000-2000 J/kg of MUCAPE from central to eastern Iowa, combined with bulk shear of 30-40 kts, will support the development of isolated to scattered severe thunderstorms with damaging winds embedded within the showers and storms. These storms appear most likely from 7 PM this evening through 5 AM Wednesday morning due to the nocturnal LLJ enhancing the shear profiles. Due to this risk, SPC has issued a Slight, level 2 of 5, risk for severe thunderstorms west of a Marengo to Cedar Rapids to Masonville line, and a Marginal, level 1 of 5, risk west of a Fairfield to Bellevue line.

An additional concern with these showers and storms is the potential for heavy rain and hydro concerns. As previously mentioned, moisture- laden air with PWATs of 2.00+ inches will be in place, which will provide ample moisture for heavy rain. In addition, vertical wind shear profiles will be oriented parallel to the boundary, which will be supportive of training storms that last over one location for several hours. This long duration and the potential for localized higher rainfall amounts in thunderstorms leads to increased risk of flash flooding despite the recent dryness. This risk will be highest west of Highway 218 in eastern Iowa, 1-2 inches of rain are expected with localized chances (30-60%) for 3+ inches. Elsewhere, rainfall totals of 0.3-1 inch are anticipated. Due to this, WPC has issued a SLight, level 2 of 5, risk for excessive rainfall for eastern Iowa west of Highway 218.

LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/

Issued at 214 PM CDT Mon Sep 7 2026

Cold front isn't expected to be out of our area until early afternoon on Wednesday, which will keep precipitation chances over much of the area through the first half of the day. We will see shower/storm coverage decrease from northwest to southeast through the morning, with best chances for precipitation in the afternoon hours for areas in western Illinois and northeastern Missouri. At this time, we are not expecting much in the way of strong-severe storms. Much of the remaining instability will have been worked through, leaving us with a shield of stratiform rain and little/no embedded thunder. Otherwise, we will see mostly cloudy conditions through the day, with temperatures in the low 80s and light west to northwest winds.

Thursday into Friday, upper level flow becomes more northwesterly as a weak wave passes through and weak ridging builds over the Central CONUS. This wave will be through our area by midday Thursday, with surface high pressure moving in behind. A brief period of quiet and seasonal weather will result, with mostly clear skies and temperatures around 80 on Thursday into Friday. Overnight temperatures will cool off a bit compared to recent nights, with most in the mid 50s. Friday, the weak ridge will pass east of the area, with southwesterly flow increasing ahead of a quickly- approaching shortwave trof. This wave is due to come through Friday night into Saturday, prompting our next chance of precipitation (30- 60% chances). Showers and storms will be possible along the associated cold front, but accumulations should be on the lower-end due to the quick movement of this wave. There remains some uncertainty, owing to moisture availability.

Saturday and beyond appear to be a continuation of potentially active weather, with us falling largely under upper level zonal to southwesterly flow. This patten would favor us falling under the path of passing shortwaves through the weekend and into next week. Thus, daily PoPs (20-40%+) are in the forecast through this stretch, with temperatures remaining above seasonal norms.

AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/

Issued at 1245 AM CDT Tue Sep 8 2026

VFR conditions are expected for the majority of the TAF period. Winds through the period will turn from southeasterly to southerly as a wave moves through the area. With this wave there is a low chance (10-30%) of decaying showers from 08/13-16Z at DBQ, which could lead to MVFR VSBYs. Higher-impact showers and storms are likely (50-80%) towards the end of the period, which will bring periods of MVFR or lower VSBYs to CID/DBQ by 09/01-02Z and at the earliest by 08/22-23Z. Once showers and storms move into the terminals, multiple hours of MVFR or lower flight conditions should be expected.

DVN WATCHES/WARNINGS/ADVISORIES

IA...None. IL...None. MO...None.